Abstract : The patent relates to a pair of compartmented cylinders providing buoyant support for a huge, heavy, undersea structure. After the compartmented cylinders and structure have been towed to the work site, flooding and evacuating selected compartments in each of the cylinders rotates them in opposite directions. When the cylinders have cleared the downward projection of the structure, it is lowered to the bottom by continued flooding and evacuating of the compartments. By rotating one of the cylinders a greater or lesser degree than the other, the undersea structure is aligned in a vertical or a desired angular relationship with respect to the bottom. The compartmented cylinders function as the supporting member for the undersea structure during construction, as a transport vehicle to the work site, and as the mechanism for deploying the structure to the bottom.